Cyanopyridone derivatives as liquid crystals

ABSTRACT

The invention relates to cyanopyridone derivatives, to their use in liquid crystal media, liquid crystal devices, anisotropic polymers, optical, electrooptical, decorative, security, cosmetic, diagnostic, pharmaceutic, electric, electronic, charge transport, semiconductor, optical recording, electroluminescent, photoconductor and electrophotographic applications, and to liquid crystal media, polymers and displays comprising them.

FIELD OF THE INVENTION

The invention relates to cyanopyridone derivatives, to their use inliquid crystal media, liquid crystal devices, anisotropic polymers,optical, electrooptical, decorative, security, cosmetic, diagnostic,pharmaceutic, electric, electronic, charge transport, semiconductor,optical recording, electroluminescent, photoconductor andelectrophotographic applications, and to liquid crystal media, polymersand displays comprising them.

BACKGROUND AND PRIOR ART

For use in liquid crystal display (LCD) applications it is oftenrequired to have available liquid crystal (LC) compounds and media witha high positive value of the dielectric anisotropy Δε, which in turnrequires that the material has a large molecular dipole. Until now,materials with terminal cyano groups have been used extensively for thispurpose, as the cyano group is of high polarisability.

Thus, LC compounds with a Δε of +20 or more and having a terminal cyanogroup are widely known in prior art. For many applications, however, LCcompounds and media with still higher Δε are needed. Furthermore, thecompounds known from prior art do often have unfavourable properties,like high melting points, smectic phases or unfavourable vaues of thebirefringence.

Consequently, there is still a need for materials with high polarity andpositive Δε that can be used in LC media to increase the value of Δε,without negatively affecting the other properties of the media, such asthe LC phase range.

The inventors of the present invention have found that the abovementioned drawbacks can be overcome by providing cyanopyridonederivatives as claimed in the present invention. These compounds haveadvantageous properties and are suitable for use in optical,electrooptical, security, electronic, charge transport, semiconductor,optical recording, electroluminescent, photovoltaic orelectrophotographic applications, in particular in LC media and LCdevices.

WO 88/07992 describes5-cyano-1,6-dihydro-6-oxo-2-(4-octyloxyphenyl)-pyridine as intermediatein the preparation of cyanopyridines for ferroelectric LC media.

EP 0 180 188 describes the use of 3,4,5-trimethoxybenzoic acid5-cyano-1,6-dihydro-6-oxo-2-pyridinyl ester for use in pharmaceuticcompositions to increase the anticancer activity of 3-fluorouracil andrelated compounds.

DeJohn et al., J. Heterocycl. Chem. 1983, 20(5), 1295-1302 describe5-cyano-1,6-dihydro-6-oxo-2-[2-(4-methoxyphenyl)ethenyl]pyridine. Ratebet al., J. Chem Soc. 1960, 1426-1430 describe3-cyano-1,2-dihydro-6-(4-methoxystyryl)-2-oxo-isonicotinic acid ethylester and its substituted derivatives.

One aim of the present invention is to provide novel cyanopyridonederivatives with improved properties, especially mesogenic or liquidcrystalline cyanopyridones with a rod-shaped molecular structure andpolymerisable cyanopyridones.

Another aim is to provide advantageous uses for the novel cyanopyridonederivatives, such as liquid crystal media, liquid crystal devices,anisotropic polymers, optical, electrooptical, decorative, security,cosmetic, pharmaceutic, diagnostic, electric, electronic, chargetransport, semiconductor, optical recording, electroluminescent,photoconductor and electrophotographic applications.

Another aim of the invention is to provide improved LC media and LCpolymers with high polarity and high positive values of the dielectricanisotropy that do not have the drawbacks of LC media known from priorart.

Other aims of the present invention are immediately evident to theperson skilled in the art from the following detailed description.

SUMMARY OF THE INVENTION

The invention relates to the use of a compound comprising at least one5-cyanopyridon-2-yl group (cyanopyridone derivative) as mesogenic orliquid crystalline material, in liquid crystal media, liquid crystaldevices, anisotropic polymers, optical, electrooptical, decorative,security, cosmetic, diagnostic, electric, electronic, charge transport,semiconductor, optical recording, electroluminescent, photoconductor andelectrophotographic applications.

The invention further relates to the use of a compound comprising atleast one 5-cyanopyridon-2-yl group for the applications describedabove, wherein the 5-cyanopyridon-2-yl group is selected of formula (1)

wherein R¹, R² and R³ are independently of each other H or an optionallysubstituted aliphatic, cycloaliphatic or aromatic group with up to 20 Catoms that optionally comprises one or more hetero atoms and optionallycomprises fused rings.

The invention further relates to the uses as described above, whereinthe cyanopyridone derivative is selected of formula I

wherein R¹, R² and R³ are as defined in formula (1),

-   A¹ and A² are independently of each other an aromatic or alicyclic    ring, or a group comprising two or more fused aromatic or alicyclic    rings, wherein these rings optionally contain one or more hetero    atoms selected from N, O and S, and are optionally mono- or    polysubstituted by R,-   Z¹ and Z² are independently of each other —O—, —S—, —CO—, —COO—,    —OCO—, —S—CO—, —CO—S—, —O—COO—, —CO—NR⁰—, —NR⁰—CO—, —OCH₂—, —CH₂O—,    —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —CH₂CH₂—, —CF₂CH₂—,    —CH₂CF₂—, —CF₂CF₂—, —CH═N—, —N═CH—, —N═N—, —CH═CR⁰—, —CY¹═CY²—,    —C≡C—, —CH═CH—COO—, —OCO—CH═CH— or a single bond,-   Y¹ and Y² are independently of each other H, F, Cl or CN,-   R is H, F, Cl, Br, I, CN, NO₂, NCS, SF₅ or alkyl which is straight    chain or branched, has 1 to 20 C-atoms, is unsubstituted, mono- or    poly-substituted by F, Cl, Br, I or CN, and in which one or more    non-adjacent CH₂ groups are optionally replaced, in each case    independently from one another, by —O—, —S—, —NH—, —NR⁰—, —SiR⁰R⁰⁰—,    —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —CY¹═CY²— or —C≡C— in    such a manner that O and/or S atoms are not linked directly to one    another, or R denotes P-Sp,-   R⁰ and R⁰⁰ are independently of each other H or alkyl with 1 to 12    C-atoms,-   P is a polymerisable or reactive group,-   Sp is a spacer group or a single bond, and-   m is 0, 1 or 2.

The invention further relates to mesogenic or liquid crystallinecyanopyridone derivatives, in particular compounds comprising at leastone group of formula (1) as defined above.

The invention further relates to novel cyanopyridone derivatives offormula I, in particular to mesogenic or liquid crystallinecyanopyridone derivatives of formula I

wherein A¹, A², Z¹, Z², R, R¹, R², R³ and m are as defined above, withthe provisos that

-   a) if m is 0, R¹, R² and R³ are H and Z¹ is a single bond, then A¹-R    is different from 4-alkylphenyl or 4-alkoxyphenyl,-   b) if m is 0, R¹, R² and R³ are H and Z¹ is COO or CH═CH, then A¹-R    is different from 4-methoxyphenyl, 3,4-dimethoxyphenyl or    3,4,5-trimethoxyphenyl,-   c) if m is 0, R¹ and R³ are H, R² is carboxyethyl and Z¹ is CH═CH,    CH═C(CH₃) or CH═C(C₆H₅), then A¹-R is different from phenyl or    4-methoxyphenyl.

The invention further relates to an LC medium comprising at least onecyanopyridone derivative which preferably comprises at least one groupof formula (1) and is very preferably selected of formula I.

The invention further relates to a polymerisable LC medium comprising atleast one cyanopyridone derivative and at least one polymerisablecompound, wherein said cyanopyridone derivative preferably comprises atleast one group of formula (1) and is very preferably selected offormula I, and said polymerisable compound can be said cyanopyridonederivative or an additional compound.

The invention further relates to a polymer obtained by polymerising acyanopyridone derivative or a polymerisable LC medium as described aboveand below.

The invention further relates to an anisotropic polymer obtained bypolymerising a cyanopyridone derivative or a polymerisable LC medium asdescribed above and below in its oriented state, preferably in form of afilm.

The invention further relates to the use of a cyanopyridone derivative,a liquid crystal medium, a polymer or a polymer film as described aboveand below in electrooptical displays, liquid crystal displays, opticalfilms, polarisers, compensators, beam splitters, reflective films,alignment layers, colour filters, holographic elements, hot stampingfoils, coloured images, decorative or security markings e.g. forconsumer objects or documents of value, LC pigments, adhesives,synthetic resins with anisotropic mechanical properties, cosmetics,pharmaceutics, diagnostics, nonlinear optics, optical informationstorage, as chiral dopants, in electronic devices like for example fieldeffect transistors (FET) as components of integrated circuitry, as thinfilm transistors in flat panel display applications or for RadioFrequency Identification (RFID) tags, or in semiconducting componentsfor organic light emitting diode (OLED) applications, electroluminescentdisplays or backlights of LCDs, for photovoltaic or sensor devices, aselectrode materials in batteries, as photoconductors, or forelectrophotographic applications or electrophotographic recording.

The invention further relates to an LC device comprising a cyanopyridonederivative or an LC medium, polymer or polymer film as described aboveand below.

DEFINITION OF TERMS

The terms ‘liquid crystalline or mesogenic material’ or ‘liquidcrystalline or mesogenic compound’ means materials or compoundscomprising one or more rod-shaped, lath-shaped or disk-shaped mesogenicgroups, i.e., groups with the ability to induce LC phase behaviour. Thecompounds or materials comprising mesogenic groups do not necessarilyhave to exhibit an LC phase themselves. It is also possible that theyshow LC phase behaviour only in mixtures with other compounds, or whenthe mesogenic compounds or materials, or the mixtures thereof, arepolymerised.

The terms ‘polymerisable’ and ‘reactive’ include compounds or groupsthat are capable of participating in a polymerisation reaction, likeradicalic or ionic chain polymerisation, polyaddition orpolycondensation, and reactive compounds or reactive groups that arecapable of being grafted for example by condensation or addition to apolymer backbone in a polymeranaloguous reaction.

The term ‘film’ includes self-supporting, i.e., free-standing, filmsthat show more or less pronounced mechanical stability and flexibility,as well as coatings or layers on a supporting substrate or between twosubstrates.

DETAILED DESCRIPTION OF THE INVENTION

The LC media and LC devices according to the present inventioncomprising one or more cyanopyridone derivatives are advantageous asthey exhibit an increased dielectric anisotropy Δε.

In particular the novel compounds of formula I are advantageous as theyexhibit a very high value of Δε the dielectric anisotropy.

Therefore, it is possible to considerably increase the value of Δε in LCmedia by using the inventive compounds even in only small amounts.

The cyanopyridone derivatives, in particular the compounds of formula I,are especially useful for a display using liquid crystals in theisotropic state, hereinafter shortly referred to as “isotropic modedisplay”, as described for example in DE 102 172 73 or WO 02/93244 A1.Thus, another object of the present invention is a display of theisotropic mode comprising at least one cyanopyridone derivative, whichis preferably a compound of formula I or of the preferred compoundsshown above and below, or comprising an LC medium comprising such acyanopyridone derivative.

Another aspect of the invention relates to polymerisable compounds offormula I, also known as reactive mesogens, and to LC polymers obtainedfrom these compounds or mixtures comprising them.

Another aspect of the invention relates to highly ordered anisotropic LCpolymer films that are obtained from polymerisable compounds or reactivemesogens of formula I, or mixtures comprising them, by aligning them intheir LC phase into uniform orientation and polymerising them in situ,e.g. by thermal or photopolymerisation.

The novel compounds of formula I have the following advantages

-   -   they are easy to prepare in excellent yield from cheap,        commercially available starting materials.    -   they are highly polar and, when appropriately substituted, show        increased dielectric anisotropy Δε=ε₁₁ −ε_(⊥) due to increased        ε₁₁.    -   they are rod shaped and are suitable as components of LC        mixtures in LCDs. The molecules themselves do not necessarily        have to exhibit an LC phase, but by being rod shaped they do not        diminish the electro-optical properties of the LC host in to        which they are dissolved.    -   their high polarity is due to the cyano and keto groups at        adjacent positions in the ring and gives the compounds high        dielectric anisotropy Δε.    -   they can also be designed to have high birefringence Δn. High Δε        and high Δn are desirable properties in LCD applications.    -   they can be used to reduce the operating voltage in LCDs, and to        modify physical properties of a mixture used for LCDs such as        birefringence, viscosity and temperature leading to improvements        in optical performance of a display device.    -   the presence of an alkyl group on the cyanopyridone ring        increases overall polarity of the system by pushing electrons        into the ring towards the electron withdrawing cyano        constituents. The alkyl substituent also gives rise to smectic        phase suppression and also lower melting points. Low melting        points are particularly important for compounds in LC mixtures        which operate at ambient temperatures.    -   they can be polymerised if appropriately substituted.

The compounds of formula I are especially suitable for use in mixturesfor LCD applications, in particular for applications using LC mixturesin the nematic or isotropic phase where high birefringence, highpolarity and high dielectric anisotropy are required.

Furthermore, the compounds of formula I can be used as reactive mesogensand can be used to make polymers or polymer films for use as opticalfilms, in particular optical retardation or compensation films,alignment layers, colour filters or polarisers in an LCD.

Another field of use of polymerisable compounds of formula I is assemiconductors or charge transport materials. These materials can beused in electronic devices like for example field effect transistors(FET) as components of integrated circuitry, as thin film transistors inflat panel display applications or for Radio Frequency Identification(RFID) tags, or in semiconducting components for organic light emittingdiode (OLED) applications, electroluminescent displays or backlights ofLCDs, for photovoltaic or sensor devices.

It is also possible to co-polymerise compounds of formula I via group Pwith other polymerisable mesogenic monomers, as well as with othercompounds of formula I, in order to induce or enhance LC phasebehaviour.

The LCDs according to the present invention are for example conventionalLCDs, in particular those of the DAP (deformation of aligned phases) orVA (vertically aligned) mode, like e.g. ECB (electrically controlledbirefringence), CSH (colour super homeotropic), VAN or VAC (verticallyaligned nematic or cholesteric) displays, MVA (multi-domain verticallyaligned) or PVA (patterned vertically aligned) displays, in displays ofthe bend mode or hybrid type displays, like e.g. OCB (opticallycompensated bend cell or optically compensated birefringence), R-OCB(reflective OCB), HAN (hybrid aligned nematic) or pi-cell (π-cell)displays, furthermore in displays of the TN (twisted nematic), HTN(highly twisted nematic) or STN (super twisted nematic), in AMD-TN(active matrix driven TN) displays, in displays of the IPS (in planeswitching) mode which are also known as ‘super TFT’ displays, or indisplays using liquid crystals in the isotropic state, hereinaftershortly referred to as “isotropic mode display”, as described forexample in DE 102 172 73 and WO 02/93244 A1.

Especially preferred are TN, STN and isotropic mode displays.

The compounds according to the present invention may also be used forapplications in the cosmetic, pharmaceutic and diagnostic sector.Possible pharmaceutical applications include for example the use asantineoplastic potentiator in compositions to increase the anticanceractivity of 5-fluorouracil or related compounds.

Particularly preferred are compounds of formula I, wherein

-   -   Z¹ is —O—, —COO—, —OCO—, —OCOO—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—,        —C≡C— or —CH═CH—, most preferably —COO— or —OCO—,    -   Z¹ is different from a single bond,    -   A¹ is phenylene that is optionally substituted by one or more        groups R¹,    -   R is P-Sp-,    -   R is alkyl or alkoxy with 1 to 12, preferably 1 to 8 C-atoms or        alkenyl, alkenyloxy or alkinyl with 2 to 12, preferably 2 to 7        C-atoms,    -   Sp is alkylene with 1 to 12 C atoms which is optionally mono- or        polysubstituted by F and wherein one or more non-adjacent CH₂        may be replaced, in each case independently from one another, by        —O—, —CH═CH— or —C≡C—, and that is linked to A¹ or A² via a        group selected from —O—, —COO—, —OCO—, —OCOO— and a single bond.    -   Sp is single bond,    -   m is 0 or 1,

A¹ and A² are independently of each other an aromatic or alicyclic ring,preferably a 5-, 6- or 7-membered ring, or a group comprising two ormore, preferably two or three, fused aromatic or alicyclic rings,wherein these rings optionally contain one or more hetero atoms selectedfrom N, O and S, and are optionally mono- or polysubstituted with L,wherein L is F, Cl, Br, CN, OH, NO₂, or an alkyl, alkoxy, alkylcarbonylor alkoxycarbonyl group with 1 to 12 C atoms, wherein one or more Hatoms are optionally replaced by F or Cl.

L is preferably F, Cl, CN, OH, NO₂, CH₃, C₂H₅, OCH₃, OC₂H₅, COCH₃,COC₂H₅, COOCH₃, COOC₂H₅, CF₃, OCF₃, OCHF₂ or OC₂F₅, in particular F, Cl,CN, CH₃, C₂H₅, OCH₃, COCH₃ or OCF₃, most preferably F, Cl, CH₃, OCH₃ orCOCH₃.

Preferred groups A¹ and A² are for example furan, pyrrol, thiophene,oxazole, thiazole, thiadiazole, imidazole, phenylene, cyclohexylene,cyclohexenylene, pyridine, pyrimidine, pyrazine, azulene, indane,naphthalene, tetrahydronaphthalene, anthracene and phenanthrene.

Particularly preferably A¹ and A² are selected from furane-2,5-diyl,thiophene-2,5-diyl, thienothiophene-2,5-diyl,dithienothiophene-2,6-diyl, pyrrol-2,5-diyl, 1,4-phenylene,azulene-2,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl,naphthalene-2,6-diyl, 1,2,3,4-tetrahydro-naphthalene-2,6-diyl,indane-2,5-diyl, or 1,4-cyclohexylene wherein one or two non-adjacentCH₂ groups are optionally replaced by O and/or S, wherein these groupsare unsubstituted, mono- or polysubstituted by L as defined above.

Preferably the group -A¹-(Z²-A²)_(m)- contains only monocyclic groups A¹and A². Very preferably the group -A¹-(Z²-A²)_(m)- is a group with oneor two 5- or 6-membered rings.

Preferred subformulae for -A-(Z²-A²)_(m)- are listed below. For reasonsof simplicity, Phe in these groups is 1,4-phenylene, PheL is a1,4-phenylene group which is substituted by 1 to 4 groups L as definedabove, Cyc is 1,4-cyclohexylene, Pyd is pyridine-2,5-diyl and Pyr ispyrimidine-2,5-diyl. The following list of preferred groups-A¹-(Z²-A²)_(m)- is comprising the subformulae II-1 to II-16 as well astheir mirror images,-Phe-  II-1-Pyd-  II-2-Pyr-  II-3-PheL-  II-4-Cyc-  II-5-Phe-Z-Cyc-  II-6-Cyc-Z-Cyc-  II-7-PheL-Cyc-  II-8-Phe-Z-Phe-  II-9-Phe-Z-Pyd-  II-10-Pyd-Z-Phe-  II-11-Phe-Z-Pyr-  II-12-Pyr-Z-Phe-  II-13-PheL-Z-Phe-  II-14-PheL-Z-Pyd-  II-15-PheL-Z-Pyr-  II-16-Pyr-Z-Pyd-  II-17-Pyd-Z-Pyd-  II-18-Pyr-Z-Pyr-  II-19-PheL-Z-PheL-  II-20

In these preferred groups Z has the meaning of Z¹ as given in formula I.Preferably Z is —COO—, —OCO—, —CH₂CH₂—C≡C— or a single bond.

Very preferably -A¹-(Z-A²)_(m)- is selected from the following formulaeand their mirror images

wherein L has the meaning given above, R¹ is as defined for formula Iand r is 0, 1, 2, 3 or 4, preferably 0, 1 or 2.

The group

in these preferred formulae is very preferably Denotin

furthermore

with L having each independently one of the meanings given above.Especially preferred compounds of formula I comprise at least one group

wherein r is 1.

Further preferred compounds of formula I comprise at least two groups

wherein r is 1 and/or at least one group

wherein r is 2.

If R is an alkyl or alkoxy radical, i.e. where the terminal CH₂ group isreplaced by —O—, this may be straight-chain or branched. It ispreferably straight-chain, has 2, 3, 4, 5, 6, 7 or 8 carbon atoms andaccordingly is preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl,octyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, or octoxy,furthermore methyl, nonyl, decyl, undecyl, dodecyl, tridecyl,tetradecyl, pentadecyl, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy ortetradecoxy, for example.

Oxaalkyl, i.e. where one CH₂ group is replaced by —O—, is preferablystraight-chain 2-oxapropyl (=methoxymethyl), 2- (=ethoxymethyl) or3-oxabutyl (=2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-, 3-, 4-, or5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-,7-, 8- or 9-oxadecyl, for example.

If R is an alkyl group wherein one or more CH₂ groups are replaced by—CH═CH—, this may be straight-chain or branched. It is preferablystraight-chain, has 2 to 10 C atoms and accordingly is preferably vinyl,prop-1-, or prop-2-enyl, but-1-, 2- or but-3-enyl, pent-1-, 2-, 3- orpent-4-enyl, hex-1-, 2-, 3-, 4- or hex-5-enyl, hept-1-, 2-, 3-, 4-, 5-or hept-6-enyl, oct-1-, 2-, 3-, 4-, 5-, 6- or oct-7-enyl, non-1-, 2-,3-, 4-, 5-, 6-, 7- or non-8-enyl, dec-1-, 2-, 3-, 4-, 5-, 6-, 7-, 8- ordec-9-enyl.

Especially preferred alkenyl groups are C₂-C₇-1 E-alkenyl,C₄-C₇-3E-alkenyl, C₅-C₇-4-alkenyl, C₆-C₇-5-alkenyl and C₇-6-alkenyl, inparticular C₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl and C₅-C₇-4-alkenyl.Examples for particularly preferred alkenyl groups are vinyl,1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl,3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl,4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groupshaving up to 5 C atoms are generally preferred.

If R is an alkyl group, wherein one CH₂ group is replaced by —O— and oneby —CO—, these radicals are preferably neighboured. Accordingly theseradicals together form a carbonyloxy group —CO—O— or an oxycarbonylgroup —O—CO—. Preferably this group R is straight-chain and has 2 to 6 Catoms.

It is accordingly preferably acetyloxy, propionyloxy, butyryloxy,pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl,butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl,2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl,3-propionyloxypropyl, 4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl,propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl,ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl,2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl,2-(propoxy-carbonyl)ethyl, 3-(methoxycarbonyl)propyl,3-(ethoxycarbonyl)propyl, 4-(methoxycarbonyl)-butyl.

If R is an alkyl group, wherein two or more CH₂ groups are replaced by—O— and/or —COO—, it can be straight-chain or branched. It is preferablystraight-chain and has 3 to 12 C atoms. Accordingly it is preferablybis-carboxy-methyl, 2,2-bis-carboxy-ethyl, 3,3-bis-carboxy-propyl,4,4-bis-carboxy-butyl, 5,5-bis-carboxy-pentyl, 6,6-bis-carboxy-hexyl,7,7-bis-carboxy-heptyl, 8,8-bis-carboxy-octyl, 9,9-bis-carboxy-nonyl,10,10-bis-carboxy-decyl, bis-(methoxycarbonyl)-methyl,2,2-bis-(methoxycarbonyl)-ethyl, 3,3-bis-(methoxycarbonyl)-propyl,4,4-bis-(methoxycarbonyl)-butyl, 5,5-bis-(methoxycarbonyl)-pentyl,6,6-bis-(methoxycarbonyl)-hexyl, 7,7-bis-(methoxycarbonyl)-heptyl,8,8-bis-(methoxycarbonyl)-octyl, bis-(ethoxycarbonyl)-methyl,2,2-bis-(ethoxycarbonyl)-ethyl, 3,3-bis-(ethoxycarbonyl)-propyl,4,4-bis-(ethoxycarbonyl)-butyl, 5,5-bis-(ethoxycarbonyl)-hexyl.

If R is an alkyl or alkenyl group that is monosubstituted by CN or CF₃,it is preferably straight-chain. The substitution by CN or CF₃ can be inany desired position.

If R is an alkyl or alkenyl group that is at least monosubstituted byhalogen, it is preferably straight-chain. Halogen is preferably F or Cl,in case of multiple substitution preferably F. The resulting groupsinclude also perfluorinated groups. In case of monosubstitution the F orCl substituent can be in any desired position, but is preferably inω-position. Examples for especially preferred straight-chain groups witha terminal F substituent are fluormethyl, 2-fluorethyl, 3-fluorpropyl,4-fluorbutyl, 5-fluorpentyl, 6-fluorhexyl and 7-fluorheptyl. Otherpositions of F are, however, not excluded.

Halogen means F, Cl, Br and I and is preferably F or Cl.

R can be a polar or a non-polar group. In case of a polar group, it isselected from CN, SF₅, halogen, OCH₃, SCN, COR⁵, COOR⁵ or a mono- oligo-or polyfluorinated alkyl or alkoxy group with 1 to 4 C atoms. R⁵ isoptionally fluorinated alkyl with 1 to 4, preferably 1 to 3 C atoms.Especially preferred polar groups are selected of F, Cl, CN, OCH₃,COCH₃, COC₂H₅, COOCH₃, COOC₂H₅, CF₃, CHF₂, CH₂F, OCF₃, OCHF₂, OCH₂F,C₂F₅ and OC₂F₅, in particular F, Cl, CN, CF₃, OCHF₂ and OCF₃. In case ofa non-polar group, it is preferably alkyl with up to 15 C atoms oralkoxy with 2 to 15 C atoms.

R can be an achiral or a chiral group. In case of a chiral group it ispreferably selected of formula III:

wherein

-   Q¹ is an alkylene or alkylene-oxy group with 1 to 9 C atoms or a    single bond,-   Q² is an alkyl or alkoxy group with 1 to 10 C atoms which may be    unsubstituted, mono- or polysubstituted by F, Cl, Br or CN, it being    also possible for one or more non-adjacent CH₂ groups to be    replaced, in each case independently from one another, by —C≡C—,    —O—, —S—, —NH—, —N(CH₃)—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO— or    —CO—S— in such a manner that oxygen atoms are not linked directly to    one another,-   Q³ is F, Cl, Br, CN or an alkyl or alkoxy group as defined for Q²    but being different from Q².

In case Q¹ in formula III is an alkylene-oxy group, the O atom ispreferably adjacent to the chiral C atom.

Preferred chiral groups of formula III are 2-alkyl, 2-alkoxy,2-methylalkyl, 2-methylalkoxy, 2-fluoroalkyl, 2-fluoroalkoxy,2-(2-ethin)-alkyl, 2-(2-ethin)-alkoxy, 1,1,1-trifluoro-2-alkyl and1,1,1-trifluoro-2-alkoxy.

Particularly preferred chiral groups are 2-butyl (=1-methylpropyl),2-methylbutyl, 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl,2-propylpentyl, in particular 2-methylbutyl, 2-methylbutoxy,2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy,2-octyloxy, 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl,2-hexyl, 2-octyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methoxyoctoxy,6-methyloctoxy, 6-methyloctanoyloxy, 5-methylheptyloxycarbonyl,2-methylbutyryloxy, 3-methylvaleroyloxy, 4-methylhexanoyloxy,2-chlorpropionyloxy, 2-chloro-3-methylbutyryloxy,2-chloro-4-methylvaleryloxy, 2-chloro-3-methylvaleryloxy,2-methyl-3-oxapentyl, 2-methyl-3-oxahexyl, 1-methoxypropyl-2-oxy,1-ethoxypropyl-2-oxy, 1-propoxypropyl-2-oxy, 1-butoxypropyl-2-oxy,2-fluorooctyloxy, 2-fluorodecyloxy, 1,1,1-trifluoro-2-octyloxy,1,1,1-trifluoro-2-octyl, 2-fluoromethyloctyloxy for example. Verypreferred are 2-hexyl, 2-octyl, 2-octyloxy, 1,1,1-trifluoro-2-hexyl,1,1,1-trifluoro-2-octyl and 1,1,1-trifluoro-2-octyloxy.

In addition, compounds containing an achiral branched group R mayoccasionally be of importance, for example, due to a reduction in thetendency towards crystallization. Branched groups of this type generallydo not contain more than one chain branch. Preferred achiral branchedgroups are isopropyl, isobutyl (=methylpropyl), isopentyl(=3-methylbutyl), isopropoxy, 2-methyl-propoxy and 3-methylbutoxy.

The polymerisable or reactive group P is preferably selected fromCH₂═CW¹—COO—,

CH₂═CW²—(O)_(k1)—, CH₃—CH═CH—O—, (CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—,(CH₂═CH)₂CH—O—, (CH₂═CH—CH₂)₂N—, HO—CW²W³—, HS—CW²W³—, HW²N—,HO—CW²W³—NH—, CH₂═CW¹—CO—NH—, CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—,Phe-CH═CH—, HOOC—, OCN—, and W⁴W⁵W⁶Si—, with W¹ being H, Cl, CN, phenylor alkyl with 1 to 5 C-atoms, in particular H, Cl or CH₃, W² and W³being independently of each other H or alkyl with 1 to 5 C-atoms, inparticular methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ being independentlyof each other Cl, oxaalkyl or oxacarbonylalkyl with 1 to 5 C-atoms, Phebeing 1,4-phenylene and k₁ and k₂ being independently of each other 0 or1.

Especially preferably P is a vinyl group, an acrylate group, amethacrylate group, an oxetane group or an epoxy group, especiallypreferably an acrylate or methacrylate group.

As for the spacer group Sp all groups can be used that are known forthis purpose to those skilled in the art. The spacer group Sp ispreferably of formula Sp′-X, such that P-Sp- is P-Sp′-X—, wherein

-   Sp′ is alkylene with up to 20 C atoms which may be unsubstituted,    mono- or poly-substituted by F, Cl, Br, I or CN, it being also    possible for one or more non-adjacent CH₂ groups to be replaced, in    each case independently from one another, by —O—, —S—, —NH—, —NR⁰—,    —SiR⁰R⁰⁰—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —CH═CH— or    —C≡C— in such a manner that O and/or S atoms are not linked directly    to one another,-   X is —O—, —S—, —CO—, —COO—, —OCO—, —O—COO—, —CO—NR⁰—, —NR⁰—CO—,    —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—,    —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—, —CH═N—, —N═CH—, —N═N—, —CH═CR⁰—,    —CY¹═CY²—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH— or a single bond, and-   R⁰, R⁰⁰, Y¹ and Y² have one of the meanings given above.-   X is preferably —O—, —S—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CF₂O—,    —OCF₂—, —CF₂S—, —SCF₂—, —CH₂CH₂—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—,    —CH═N—, —N═CH—, —N═N—, —CH═CR⁰—, —CY¹═CY²—, —C≡C— or a single bond,    in particular —O—, —S—, —C≡C—, —CY¹═CY²— or a single bond, very    preferably a group that is able to from a conjugated system, such as    —C≡C— or —CY¹═CY²—, or a single bond.

Typical groups Sp′ are, for example, —(CH₂)_(p)—,—(CH₂CH₂O)_(q)—CH₂CH₂—, —CH₂CH₂—S—CH₂CH₂— or —CH₂CH₂—NH—CH₂CH₂— or—(SiR⁰R⁰⁰—O)_(p)—, with p being an integer from 2 to 12, q being aninteger from 1 to 3 and R⁰ and R⁰⁰ having the meanings given above.

Preferred groups Sp′ are ethylene, propylene, butylene, pentylene,hexylene, heptylene, octylene, nonylene, decylene, undecylene,dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene,ethylene-thioethylene, ethylene-N-methyl-iminoethylene,1-methylalkylene, ethenylene, propenylene and butenylene for example.

In another preferred embodiment Sp′ is a chiral group of formula IV:

whereinQ¹ and Q³ have the meanings given in formula III, andQ⁴ is an alkylene or alkylene-oxy group with 1 to 10 C atoms or a singlebond, being different from Q¹,with Q¹ being linked to the polymerizable group P.

Further preferred are compounds with one or two groups P-Sp- wherein Spis a single bond.

In case of compounds with two groups P-Sp, each of the two polymerisablegroups P and the two spacer groups Sp can be identical or different.

Particularly preferred compounds of formula I are those of the followingformulae

wherein

-   R has one of the meanings of formula I and is preferably straight    chain alkyl, alkoxy with 1 to 8 C-atoms or alkenyl, alkenyloxy or    alkinyl with 2 to 7 C-atoms,-   R′ has one of the meanings of R¹ in formula I and is preferably H or    alkyl with 1, 2 or 3 C-atoms, very preferably H, methyl or ethyl,-   R″ has one of the meanings of R¹ in formula I and is preferably H or    alkyl with 1, 2 or 3 C-atoms, very preferably H, methyl or ethyl,-   R′″ has one of the meanings of R¹ in formula I and is preferably H    or alkyl alkoxy with 1, 2 or 3 C-atoms, very preferably H,    methyl(oxy) or ethyl(oxy),-   P has one of the meanings given above and below,-   L¹ and L² are independently of each other H or F, and-   n is an integer from 1 to 12.

The aromatic rings in the above preferred formulae are optionallysubstituted with 1, 2 or 3 groups L as defined above.

The compounds of formula I can be synthesized according to or in analogyto methods which are known per se and which are described in standardworks of organic chemistry such as, for example, Houben-Weyl, Methodender organischen Chemie, Thieme-Verlag, Stuttgart. Some specific andpreferred methods are described in the reaction schemes below. Furthermethods can be taken from the examples.

For the applications described above the LC media preferably contain atleast one compound of formula 1, and a nematic host mixture comprisingone or more nematic or nematogenic compounds.

Preferably the LC media consist of 2 to 25, preferably 3 to 15compounds, at least one of which is a compound of formula I or I1. Theother compounds, forming the nematic host mixture, are preferably lowmolecular weight liquid crystal compounds selected from nematic ornematogenic substances, for example from the known classes of theazoxybenzenes, benzylidene-anilines, biphenyls, terphenyls, phenyl orcyclohexyl benzoates, phenyl or cyclohexyl esters ofcyclohehexanecarboxylic acid, phenyl or cyclohexyl esters ofcyclohexylbenzoic acid, phenyl or cyclohexyl esters ofcyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl esters of benzoicacid, of cyclohexanecarboxylic acid and ofcyclo-hexylcyclohexanecarboxylic acid, phenylcyclohexanes,cyclohexyl-biphenyls, phenylcyclohexylcyclohexanes,cyclohexylcyclohexanes, cyclohexylcyclohexenes,cyclohexylcyclohexylcyclohexenes, 1,4-bis-cyclohexylbenzenes,4,4′-bis-cyclohexylbiphenyls, phenyl- or cyclo-hexylpyrimidines, phenyl-or cyclohexylpyridines, phenyl- or cyclo-hexylpyridazines, phenyl- orcyclohexyldioxanes, phenyl- or cyclo-hexyl-1,3-dithianes,1,2-diphenyl-ethanes, 1,2-dicyclohexylethanes,1-phenyl-2-cyclohexylethanes,1-cyclohexyl-2-(4-phenylcyclohexyl)-ethanes,1-cyclohexyl-2-biphenyl-ethanes, 1-phenyl2-cyclohexyl-phenylethanes,optionally halogenated stilbenes, benzyl phenyl ether, tolanes,substituted cinnamic acids and further classes of nematic or nematogenicsubstances. The 1,4-phenylene groups in these compounds may also belaterally mono- or difluorinated.

The most important compounds that are possible as components of these LCmixtures' can be characterized by the following formulaR′-L′-G′-E-R″wherein L′ and E, which may be identical or different, are in each case,independently from one another, a bivalent radical from the group formedby -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -B-Phe-and -B-Cyc- and their mirror images, where Phe is unsubstituted orfluorine-substituted 1,4-phenylene, Cyc is trans-1,4-cyclohexylene or1,4-cyclohexenylene, Pyr is pyrimidine-2,5-diyl or pyridine-2,5-diyl,Dio is 1,3-dioxane-2,5-diyl abd B is 2-(trans-1,4-cyclohexyl)ethyl,pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl.

G′ in these compounds is selected from the following bivalent groups—CH═CH—, —N(O)N—, —CH═CY—, —CH═N(O)—, —C≡C—, —CH₂—CH₂—, —CO—O—, —CH₂—O—,—CO—S—, —CH₂—S—, —CH═N—, —COO-Phe-COO— or a single bond, with Y beinghalogen, preferably chlorine, or —CN.

R′ and R″ are, in each case, independently of one another, alkyl,alkenyl, alkoxy, alkenyloxy, alkanoyloxy, alkoxycarbonyl oralkoxycarbonyloxy with 1 to 18, preferably 3 to 12 C atoms, oralternatively one of R′ and R″ is F, CF₃, OCF₃, Cl, NCS or CN.

In most of these compounds R′ and R″ are, in each case, independently ofeach another, alkyl, alkenyl or alkoxy with different chain length,wherein the sum of C atoms in nematic media generally is between 2 and9, preferably between 2 and 7.

Many of these compounds or mixtures thereof are commercially available.All of these compounds are either known or can be prepared by methodswhich are known per se, as described in the literature (for example inthe standard works such as Houben-Weyl, Methoden der Organischen Chemie[Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), to beprecise under reaction conditions which are known and suitable for saidreactions. Use may also be made here of variants which are known per se,but are not mentioned here.

Examples of suitable polymerisable mesogenic compounds that can be usedas comonomers together with the compounds of formula I in apolymerisable LC mixture, are disclosed for example in WO 93/22397, EP 0261 712, DE 195 04 224, WO 95/22586, WO 97/00600 and GB 2 351 734. Thecompounds disclosed in these documents, however, are to be regardedmerely as examples that shall not limit the scope of this invention.

Preferably the polymerizable LC mixture comprises at least onepolymerisable mesogenic compound having one polymerisable functionalgroup and at least one polymerisable mesogenic compound having two ormore polymerisable functional groups.

Examples of especially useful chiral and achiral polymerisable mesogeniccomonomers are shown in the following lists which should, however, betaken only as illustrative and is in no way intended to restrict, butinstead to explain the present invention:

wherein P has one of the meanings of formula I and its preferredmeanings as mentioned above, x and y are identical or different integersfrom 1 to 12, A and D are 1,4-phenylene or 1,4-cyclohexylene, v is 0 or1, Y is a polar group, R⁰ is a non-polar (or unpolar) alkyl or alkoxygroup, Ter is a terpenoid radical like e.g. menthyl, ChoI is acholesteryl group, the phenylene rings in formulae Va to Vlc may also besubstituted by 1, 2, 3 or 4 groups L¹, in particular mono- ordifluorinated, and L¹ and L² are each independently H, F, Cl, OH, CN,NO₂ or optionally alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl with 1to 7 C atoms.

The term ‘polar group’ in this connection means a group selected from F,Cl, CN, NO₂, OH, OCH₃, OCN, SCN, an optionally fluorinated carbonyl orcarboxyl group with up to 4 C atoms or a mono-, oligo- orpolyfluorinated alkyl or alkoxy group with 1 to 4 C atoms. The term‘non-polar group’ (or ‘unpolar group’) means an alkyl group with 1 ormore, preferably 1 to 12 C atoms or an alkoxy group with 2 or more,preferably 2 to 12 C atoms.

The polymerisable LC mixtures according to the present invention mayalso comprise one or more non-reactive chiral dopants in addition oralternatively to chiral polymerisable mesogenic compounds. Typicallyused chiral dopants are e.g. the commercially available R or S 811, R orS 1011, R or S 2011 or CB 15 (from Merck KGaA, Darmstadt, Germany). Verypreferred are chiral dopants with a high helical twisting power (HTP),in particular dopants comprising a sorbitol group as described in WO98/00428, dopants comprising a hydrobenzoin group as described in GB2,328,207, chiral binaphthyl derivatives as described in WO 02/94805,chiral binaphthol acetal derivatives as described in WO 02/34739, chiralTADDOL derivatives as described in WO 02/06265, and chiral dopants withat least one fluorinated linkage group and a terminal or central chiralgroup as described in WO 02/06196 and WO 02/06195.

To prepare anisotropic polymer films, the polymerisable LC mixture ispreferably coated onto a substrate, aligned and polymerised in situ, forexample by exposure to heat or actinic radiation, to fix the orientationof the LC molecules. Alignment and curing are carried out in the LCphase of the mixture. This technique is well-known in the art and isgenerally described for example in D. J. Broer, et al., Angew.Makromoli. Chem. 183, (1990), 45-66.

Alignment of the LC material can be achieved for example by treatment ofthe substrate onto which the material is coated, by shearing thematerial during or after coating, by application of a magnetic orelectric field to the coated material, or by the addition ofsurface-active compounds to the LC material. Reviews of alignmenttechniques are given for example by 1. Sage in “Thermotropic LiquidCrystals”, edited by G. W. Gray, John Wiley & Sons, 1987, pages 75-77,and by T. Uchida and H. Seki in “Liquid Crystals—Applications and UsesVol. 3”, edited by B. Bahadur, World Scientific Publishing, Singapore1992, pages 1-63. A review of alignment materials and techniques isgiven by J. Cognard, Mol. Cryst. Liq. Cryst. 78, Supplement 1 (1981),pages 1-77.

Polymerisation takes place by exposure to heat or actinic radiation.Actinic radiation means irradiation with light, like UV light, IR lightor visible light, irradiation with X-rays or gamma rays or irradiationwith high energy particles, such as ions or electrons. Preferablypolymerisation is carried out by UV irradiation at a non-absorbingwavelength. As a source for actinic radiation for example a single UVlamp or a set of UV lamps can be used. When using a high lamp power thecuring time can be reduced. Another possible source for actinicradiation is a laser, like e.g. a UV laser, an IR laser or a visiblelaser.

Polymerisation is preferably carried out in the presence of an initiatorabsorbing at the wavelength of the actinic radiation. For example, whenpolymerising by means of UV light, a photoinitiator can be used thatdecomposes under UV irradiation to produce free radicals or ions thatstart the polymerisation reaction. When curing polymerisable materialswith acrylate or methacrylate groups, preferably a radicalphotoinitiator is used, when curing polymerisable materials with vinyl,epoxide and oxetane groups, preferably a cationic photoinitiator isused. It is also possible to use a polymerisation initiator thatdecomposes when heated to produce free radicals or ions that start thepolymerisation. As a photoinitiator for radical polymerisation forexample the commercially available Irgacure 651, Irgacure 184, Darocure1173 or Darocure 4205 (all from Ciba Geigy AG) can be used, whereas incase of cationic photopolymerisation the commercially available UVI 6974(Union Carbide) can be used.

The polymerisable material can additionally comprise one or more othersuitable components such as, for example, catalysts, sensitizers,stabilizers, inhibitors, chain-transfer agents, co-reacting monomers,surface-active compounds, lubricating agents, wetting agents, dispersingagents, hydrophobing agents, adhesive agents, flow improvers, defoamingagents, deaerators, diluents, reactive diluents, auxiliaries,colourants, dyes or pigments.

The examples below serve to illustrate the invention without limitingit. In the foregoing and the following, all temperatures are given indegrees Celsius, and all percentages are by weight, unless statedotherwise. The following abbreviations are used to illustrate the liquidcrystalline phase behaviour of the compounds: K=crystalline; N=nematic;S=smectic; N*, Ch=chiral nematic or cholesteric; I=isotropic. Thenumbers between these symbols indicate the phase transition temperaturesin degree Celsius.

EXAMPLE 1

Compound (1) was prepared as shown in reaction scheme 1 above.

2,3-Difluoro-4-ethoxybenzoic acid (4.00 g, 0.02 mol),1-ethyl-1,2-dihydro-6-hydroxy-4-methyl-2-oxo-3-pyridinecarbonitrile(commercially available from Aldrich) (3.56 g, 0.02 mol) and DCC (4.12g, 0.02 mol) and a catalytic amount of dimethylaminopyridine indimethylacetamide (80 ml) were charged to a 3- neck round bottomed flaskand stirred under nitrogen at 35 degrees. Reaction progress wasmonitored by GCMS. After over night stirring, a precipitate of DCU wasremoved by filtration. The dimethylacetamide solvent was removed bydistillation and the residue was partitioned between water and DCM. Thechlorinated phase was washed, dried and evaporated. The crude productwas purified by flash column chromatography using DCM as eluant. A solidwas isolated, GCMS and NMR showed expected signals.

The compound has a melting point of 136° C.

EXAMPLE 2

Compound (2) was prepared as shown in reaction scheme 2 above.

2,6-Difluoro-4-heptynylbenzoic acid (5.00 g, 0.02 mol),1-ethyl-1,2-dihydro-6-hydroxy-4-methyl-2-oxo-3-pyridinecarbonitrile(3.56 g, 0.02 mol) and DCC (4.12 g, 0.02 mol) and a catalytic amount ofdimethylaminopyridine in dimethylacetamide (80 ml) were charged to a3-neck round bottomed flask and stirred under nitrogen at 35 degrees.Reaction procedure was monitored by TLC. After 16 h, TLC showed thereaction to have gone to completion. A white precipitate was removed byfiltration. The filtrate was washed with water. The toluene phase wasremoved, dried over sodium sulphate and evaporated to dryness on arotary evaporator. Purification was achieved by flash columnchromatography using DCM as eluant. Evaporation of the appropriatefractions gave the desired product as a grey solid. (1 spot by TLC). ¹HNMR and GCMS showed expected signals.

The compound has a melting point of 98° C.

EXAMPLE 3

Compound (3) was prepared as shown in reaction scheme 3 above.

Dimethyluracil (10.0 g, 0.071 mol), 2-cyanoacetamide (5.97 g, 0.071 mol)and sodium ethoxide (9.66 g, 0.142 mol) were stirred in ethanol (300ml). After 30 min a large amount of solid precipitate appeared. Theprecipitate was removed by filtration and recrystallised form hot water.A white solid was isolated and used without further purification in thenext step.

4-Butyloxy-2,6-difluorobenzoic acid (9.43 g, 0.041 mol),3-hydroxy-6-cyanopyrid-5-one (5.6 g, 0.041 mol), DCC (8.46 g, 0.041 mol)and a catalytic amount of dimethylaminopyridine in dimethylacetamide(100 ml) were charged to a 3-neck round bottomed flask and stirred undernitrogen at 35 degrees. Reaction progress was monitored by GCMS. After16 h, the mixture was cooled, filtered to remove DCU and then distilledto remove dimethylacetamide. The residue was partitioned between waterand ethyl acetate, the organic phase was removed, dried and evaporatedto dryness. Purification was achieved by recrystallisation from ethylacetate. GCMS showed expected signals.

1. A liquid crystalline medium, comprising at least two liquid crystalline compounds, wherein at least one of said compounds comprises a 5-cyanophridon-2-yl group is of formula I

wherein R¹, R² and R³ are independently of each other H or an optionally substituted aliphatic, cycloaliphatic or aromatic group with up to 20 C atoms that optionally comprises one or more hetero atoms and optionally comprises fused rings, A¹ and A² are independently of each other an aromatic or alicyclic ring, or a group comprising two or more fused aromatic or alicyclic rings, wherein these rings optionally contain one or more hetero atoms selected from N, O, and S, and are optionally mono- or polysubstituted by R, Z¹ and Z² are independently of each other —O—, —S—, —CO—, —COO—, —OCO—, —S—CO—, —CO—S—, —O—COO—, —CO—NR⁰—, —NR⁰—CO—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —CH₂CH₂—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—, —CH═N—, —N═CH—, —N═N—, —CH═CR⁰—, —CY¹═CY²—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH— or a single bond, Y¹ and Y² are independently of each other H, F, CI or CN, R is H, F, Cl, Br, I, CN, NO₂, NCS, SF₅ or alkyl which is straight chain or branched, has 1 to 20 C-atoms, is unsubstituted, mono- or poly-substituted by F, CI, Br, I or CN, and in which one or more non-adjacent CH₂ groups are optionally replaced, in each case independently from one another, by —O—, —S—, —NH—, NR⁰—, —SiR⁰R⁰⁰—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —CY¹═CY²— or —C═C— in such a manner that O and/or S atoms are not linked directly to one another, or R denotes P-Sp R⁰ and R⁰⁰ are independently of each other H or alkyl with 1 to 12 C-atoms, P is a polymerisable or reactive group, Sp is a spacer group or a single bond, and m is 0, 1 or
 2. 2. A cyanopyridone compound of formula I,

wherein R¹, R² and R³ are independently of each other H or an optionally substituted aliphatic, cycloaliphatic or aromatic group with up to 20 C atoms that optionally comprises one or more hetero atoms and optionally comprises fused rings, A¹ and A² are independently of each other an aromatic or alicyclic ring, or a group comprising two or more fused aromatic or alicyclic rings, wherein these rings optionally contain one or more hetero atoms selected from N, O and S, and are optionally mono- or polysubstituted by R, Z¹ and Z² are independently of each other —O—,—S—,—CO—, —COO—, —OCO—, —S—CO—,—CO—S—, —O—COO—, —CO—NR⁰—, —NR⁰—CO—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —CH₂CH₂−, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—, —CH═N—, —N═CH—, —N═N—, —CH═CR⁰—, —CY¹═CY²—, —C═C—, —CH═CH—COO—, —OCO—CH═CH— or a single bond, Y¹ and Y² are independently of each other H, F, Cl or CN, R is H, CN, NO₂, NCS, SF₅ or alkyl which is straight chain or branched, has 1 to 20 C-atoms, is unsubstituted, mono- or poly-substituted by F, CI, Br, I or CN, and in which one or more non-adjacent CH₂ groups are replaced, in each case independently from one another, by —S—, —NH—, —NR⁰—, —SiR⁰R⁰⁰—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —CY¹═CY² or —C═C— in such a manner that O and/or S atoms are not linked directly to one another, or R denotes P-Sp, R⁰ and R⁰⁰ are independently of each other H or alkyl with 1 to 12 C-atoms, P is a polymerisable or reactive group, Sp is a spacer group or a single bond, and m is 0, 1 or 2, with the proviso that if m is 0, R¹ and R³ are H, R² is carboxyethyl and Z¹ is CH═CH, CH═C(CH₃) or CH═C(C₆H₅), then A¹—R is different from phenyl or 4-methoxyphenyl.
 3. A cyanopyridone compound according to claim 2, wherein A¹ and A² are furane-2,5-diyl, thiophene-2,5-diyl, thienothiophene-2,5-diyl, dithienothiophene-2, 6-diyl, pyrrol-2,5-diyl, 1,4-phenylene, azulene-2,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, naphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, indane-2,5-diyl, or 1,4-cyclohexylene wherein one or two non-adjacent CH₂ groups are optionally replaced by O and/or S, and wherein A¹ and A² are each independently unsubstituted, mono- or polysubstituted by L, wherein L is CN, NO₂, or by an alkylcarbonyl or alkoxycarbonyl group with 1 to 12 C atoms, wherein one or more H atoms are optionally replaced by F or Cl.
 4. A cyanopyridone compound according to claim 2, wherein Z¹ is —O—, —COO—, —OCO—, —OCOO—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, —C≡C— or —CH═CH—.
 5. A cyanopyridone compound according to claim 2, wherein —A¹—(Z²—A²)_(m)— is

or a mirror image thereof, wherein L is CN, NO₂, or an alkylcarbonyl or alkoxycarbonyl group with 1 to 12 C atoms, wherein one or more H atoms are optionally replaced by F or Cl, and r is 0, 1, 2, 3 or
 4. 6. A cyanopyridone compound according to claim 2, wherein R is P-Sp.
 7. cyanopyridone compound according to claim 2, wherein R is alkyl or alkoxy with 1 to 12 or alkenyl, alkenyloxy or alkynyl with 2 to 12 C-atoms.
 8. A cyanopyridone compound according to claim 2, of the formula

or a mirror image thereof, wherein R″ and R′″ each independently have one of the meanings of R¹ in formula I, P is a polymerisable or reactive group, L¹ and L² are independently of each other H or F, and n is an integer from 1 to
 12. 9. A liquid crystal medium according to claim 1, comprising at least one polymerisable compound, which can be said cyanopyridone compound of formula I or an additional compound.
 10. A polymer obtained by polymerizing a cyanopyridone compound according to claim
 4. 11. In electrooptical displays, liquid crystal displays, optical films, polarisers, compensators, beam splitters, reflective films, alignment layers, colors filters, holographic elements, hot stamping foils, colored images, decorative or security markings, LC pigments, adhesives, synthetic resins with anisotropic mechanical properties, cosmetics, pharmaceutics, diagnostics, nonlinear optics, optical information storage, chiral dopants, electronic devices, components of integrated circuitry, thin film transistors in flat panel display applications, Radio Frequency Identification (RFTD) tags, semiconducting components for organic light emitting diode (OLED) applications, electroluminescent displays, backlights of LCDs, photovoltaic or sensor devices, batteries, photoconductors, or electrophotographic recording media comprising a liquid crystalline medium, the improvement wherein the medium is one according to claim
 1. 12. An electrooptical device, comprising a liquid crystal medium, according to claim
 1. 13. The liquid crystal device according to claim 12, which is a TN or STN display or a display using liquid crystals in the isotropic phase.
 14. A polymer obtained by polymerizing a liquid crystalline medium according to claim
 9. 15. A polymer according to claim 10, which polymer is anisotropic.
 16. A polymer according to claim 14, which polymer is anisotropic.
 17. A cyanopyridone compound of formula I,

wherein R¹, R² and R³ are independently of each other H or an optionally substituted aliphatic, cycloaliphatic or aromatic group with up to 20 C atoms that optionally comprises one or more hetero atoms and optionally comprises fused rings, A¹ and A² are independently of each other an aromatic or alicyclic ring, or a group comprising two or more fused aromatic or alicyclic rings, wherein these rings optionally contain one or more hetero atoms selected from N, O and S, and are optionally mono- or polysubstituted by R, Z¹ Z² are independently of each other —O—, —S—, —CO—, —COO—, —OCO—, —S—CO—, —CO—S—, —O—COO—, —CO—NR⁰—, —NR⁰—CO—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—,—CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —CH₂CH₂—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—, —CH═N—, —N═CH—, —N═N—, —CH═CR⁰—, —CY¹═CY²—, —C═C—, —CH═CH—COO—, —OCO—CH═CH— or a single bond, Y¹ and Y² are independently of each other H, F, Cl or CN, R is H, CN, NO₂, NCS, SF₅ or P-Sp, R⁰ and R⁰⁰ are independently of each other H or alkyl with 1 to 12 C-atoms, P is a polymerisable or reactive group, Sp is a spacer group or a single bond, and m is 0, 1 or
 2. 18. The liquid crystalline medium according to claim 1, wherein R is H, CN, NO₂, NCS, SF₅ or alkyl which is straight chain or branched, has 1 to 20 C-atoms, is unsubstituted, mono— or poly-substituted by F, Cl, Br, I or CN, and in which one or more non-adjacent CH₂ groups are replaced, in each case independently from one another, by —S—, —NH—, —NR⁰—, —SiR⁰R⁰⁰—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —CY¹═CY²— or —C═C— in such a manner that O and/or S atoms are not linked directly to one another, or R denotes P-Sp.
 19. The liquid crystalline medium according to claim 1, wherein R is H, CN, NO₂, NCS, SF₅ or P-Sp. 